Diffusive Gradients in Thin-Films Technique as a Tool for Matrix Separation and Preconcentration for Sensitive Determination of Cd and Pb in Table Salt.

Herein, we developed a sensitive and accurate analytical methodology based on diffusive gradients in thin-films (DGT) technique for matrix separation and preconcentration of Cd and Pb from table salt solution prior to their quantification by graphite furnace atomic absorption spectrometry (GFAAS). The methodology relies on the passive accumulation of the analytes from an aqueous table salt solution over a 24-h period using a relatively simple and inexpensive tool. The linear accumulation of Cd and Pb during a 24 h DGT deployment was evaluated, with determination coefficients (R 2) of 0.9939 and 0.9887, respectively. The performance parameters of the proposed methodology were evaluated in accordance with the requirements specified in Commission Decision 2002/657/EC and Commission Regulations 2023/915/EU, 2011/836/EU, and 2007/333/EC. The limits of detection for Cd and Pb in salt samples were determined to be 38 and 81 μg kg-1, respectively. The method demonstrated trueness values ranging from 85% to 92%, precision expressed as relative standard deviations between 11.0% and 13.1%, and combined standard measurement uncertainties of 13.2% for Cd and 14.0% for Pb. These performance characteristics satisfy the minimum requirements mandated for analytical methods employed in official laboratories for the quantification of Cd and Pb in food matrices. The validated method was applied to the analysis of 10 types of refined and unrefined table salt from Romanian markets. In two samples, the Pb concentration exceeded the maximum level established by Commission Regulations 2023/915/EU. The proposed method shows good analytical potential and can be easily implemented in control laboratories.